The invention is in the field of fluorescent tube mounting sockets or bases, and particularly addresses base adapters which enable a fluorescent tube to be mounted in a fixture designed for incandescents, such as the ubiquitous threaded light bulb socket. A companion application for an invention entitled, FLUORESCENT LIGHT BALLAST LAMP MOUNTING ASSEMBLY CONSTRUCTION filed on Feb. 10, 1992 with Ser. No. 832,988 represents the developmental predecessor of the invention set forth in this disclosure. The device of that disclosure minimizes the profile of the ballast housing in several ways to permit the base to be mounted in more confined spaces than is presently possible.
It is well known that compact fluorescent lamps designed to replace incandescents can save up to 75% on energy consumption compared to incandescent lamps of the same lumen output, and have lifespans eight- to ten-times greater. Such fluorescent lamps, in various size, shape and wattage configurations are commercially available from lamp manufacturers such as Phillips Lighting, General Electric, Osram Sylvania, and Panasonic.
Most of these adaptors are re-usable, being equipped with built-in ballasts and screw bases permitting replacement of the lamps alone, for easy and minimally expensive conversion of incandescent lamp fixtures to fluorescent. However, since most installations where such adaptors would be implemented were designed for use with a relatively compact light bulb, existing adaptors cannot handle the spacial constraints of many conversion situations. The following patents are representative of current adaptors:
______________________________________ 1. 4,414,489 11/1983 Young 315/51 2. 4,570,105 2/1986 Engel 315/58 3. 4,623,823 11/1986 Engel 315/58 4. 4,683,402 7/1987 Aubrey 313/318 5. 4,746,840 5/1988 Lam 315/56/58 6. 4,939,420 7/1990 Lam 315/56/58 ______________________________________
For example, the devices disclosed in U.S. Pat. Nos. 4,683,402 and 4,495,443 cannot fit into recessed fixtures with reflectors designed for horizontally mounted pear-shaped incandescent light bulbs as the side-mounted ballasts need more clearance in order to be rotated into place on installation.
The adaptors of U.S. Pat. Nos. 4,570,105 and 4,683,402, cannot fit into lamp shade harps due to bulky cylindrical ballast housing.
U.S. Pat. Nos. 4,939,420 and 4,746,840 illustrate adapters which are made solely for use as fluorescent reflector lamps lack versatility. Neither of these lamps will fit in existing lamps having shade-mounting harps.
There are considerations other than, but related to, spacial constraints. For example, the base of the compact fluorescent lamp is the hottest spot on the lamp and should not be enclosed any more than is absolutely necessary. Certainly it shouldn't be embedded into and encompassed by the housing of the ballast, as it would be unsafe and would reduce the lamp's service life. However., U.S. Pat. Nos. 4,570,105 and 4,623,823 use toroidal ballasts that enclose this hot spot. U.S. Pat. No. 4,683,402 has a recessed ballast housing which also imbeds the lamp base into the ballast. These units do not provide the airspace or ventilation needed for optimal lifespan.
The temperature of the lamp base can reach 150 C. degrees, and the highest temperatures are generally reached at the end of lamp life. In this condition, the lamp no longer starts and maximum energy is dissipated on the lamp base without producing light. These and other adaptors that imbed the fluorescent lamp base in the ballast are failure-prone designs which create temperatures considerably in excess of the recommendations of lamp manufacturers, causing early deterioration and failure of lamp starters and the ballast components. The destructive effect of heat is especially acute when the lamp is mounted in the base-up position, as on a ceiling, as the rising heat pools around the hot spot and accelerates the deterioration.
The purpose of having re-usable adaptors is obviously to require replacement of only the bare tube, when it burns out, and not a lot of perfectly good electronic components. But if the adaptor generates such high temperatures at the lamp base that the tube and the ballast suffer early failure, the economic aim of reusable adaptors is defeated.
There is a need for more user-friendly adaptors that can be easily installed without modifying existing light fixtures (which are generally unmodifiable anyway), are compatible with modern compact fluorescent lamps, fit into the limited spaces which were designed for the smaller sized incandescent lamps, and which do not destroy the fluorescent tube or ballast prematurely through overheating.